Metal working lubricant



ilnited rates Free 3,079,340 METAL WORKWG LUBRICANT Thomas E. Reamer, El Cerrito, Califl, assignor to Shell Oil Company, a corporation of Delaware No Drawing. Filed Get. 5, 1959, Ser. No. 844,211 9 Claims. (Cl. 25233.6)

This invention relates to aqueous base metal-working lubricating compositions. More particularly, it relates to a water-base metal cutting fluid.

It is well known in the art that water base fluids possess good cooling properties for processing metals, but that they lack the lubricity and extreme pressure properties of oil base lubricants and usually cause corrosion. On the other hand, oil base lubricants are inferior coolants and are costly.

The art discloses various means of imparting rust inhibiting and extreme pressure properties to water base metal-working lubricants, but with little success. Among the materials commonly used for this purpose are watersoluble non-ionic compounds, such as alkyl phenolethylene ox'de reaction products, tallow, fatty acids, soaps,

such as sodium or potassium oleate or sulfonate, in combination with water-soluble alkali metal compounds and mixtures thereof, such as the nitrites, phosphates, carbonates, or chromates, e.g., mixtures of sodium nitrite and sodium phosphate, or mixtures of sodium nitriteand sodium carbonate. Water-oil emulsions additionally present a dermatitis and stability problem upon use and are generally undesirable because of their opaqueness thus making it difficult to observe the machining process.

It is an object of this invention to provide a cutting fluid having both good cooling and good lubricating properties. Another object of the invention is to provide a non-corrosive aqueous cutting solution. Still another object of the invention is to provide a stable, non-corrosive, aqueous cutting composition free of ingredients capa ble of causing dermatitis infections. Another object of the invention is to provide a multi-functional metal working lubricant useful at high speeds, heavy loads, high pressures and high temperatures.

The above and other objects are attained in accordance with the present invention by an aqueous medium, such as water containing from about 0.05 to about moles per liter (molar=l\ i), preferably from 0.1 to 1 mole each of (l) a water-soluble alkali metal compound containIng at least one sulfur atom in the molecule, preferably in an oxidized state, and (2) a water-soluble reducing agent containing at least a group selected from hydroxyl and amino groups, a preferred class of compounds being amino and hydroxy-containing compounds, for example,"

hydroxylamine. The final water-base fluid should have a pH of at least 7, preferably between 8 and 11.

The combination of the above additives functions in a particular manner to produce an outstanding extreme pressure water base metal-working fluid.

The water-soluble alkali metal compounds which must contain sulfur in the molecule include sodium, lithium or potassium sulfur-containing salts, the anionic portion being either an inorganic sulfur-containing anion, preferably in an oxidized state, such as a sulfate, persulfate, thiosulfate, sulfoxylate, dithionate, as well as sulfide or hydrosulfide or an organic sulfur-containing anion such as mercaptocarboxylate, thiocarboxylate and mixtures thereof. The water-soluble alkali metal organic sulfurcontaining salts include, sodium, lithium or potassium salts of mercapto monoand poly-carboxylic acids such as sodium, lithium or potassium mercaptoacetate, mercaptoproprionate, mercaptosuccinate, mercaptoglutarate and mercaptoadipate; sodium, lithium or potassium salts of monoor polysulfide-containing carboxylic acids such as sodium, lithium or potassium salts of C alkyl thio C alkylcarboxylic acid, e.g., methylthioacetic acid, ethylthioacetic acid, ethylthiopro-pionic acid, methyldithioacctic acid, ethyldithioacetic acid; sulfur-containing dicarboxylic acids, e.g., thiodiacetic acid, thiodipropionic acid, dithiodiacetic acid, and the like. The salts which are preferred are sodium mercaptoacetate, mercaptosuccinate, thiodiacetate, thiodipropionate, dithiodiacetate and mixtures thereof.

The water-soluble hydroxy-containing reducing agent includes inorganic compounds such as hydroxylamine and organic compounds such as water-soluble amino compounds such as phenyl hydrozine hydrochloride, phenyl hydroxylamine, aliphatic or aromatic polyhydroxyl-containing compounds such as carbohydrates, e.g., glucose, lactose; aromatic polyhydroxyl-containing compounds such as resorcinol, pyrogallol, phloroglucinol and the like. i In cases'where the-metal being worked is extremely susceptible to corrosion or extremely difiicult frictional conditions are encountered, the addition of from 0.5% to 10%, preferably 1% to 5% each of an alkanolamine corrosion inhibitor such as mono, di or triethanolamine, mono-, di-, or tripropanolamine, etc, or the like; and as an antifriction agent a water-soluble hetero copolymeric alkylene glycol, ether or e or thereof, wherein the different oxyalkylene units are substantially randomly distributed throughout the entire polyoxyalkylene chain.

5 The water-soluble hetero copolymer improves the antifrictional properties of compositions of the present invention, particularly under slow sliding conditions. On the other hand, other non-ionic polymeric compounds such as alkyl phenol-ethylene oxide reaction products, block copolymers of dissimilar alkylene oxides and their derivatives such as are commercially available under the trade name of Pluronics and the like produce undesirable frictional problems, foaming, instability and the like. I

The water-miscible hetero-copolymer polyalkylene oxide fluids also enhance the load carrying properties of the composition of the present invention. The above oxides are hetero-copolymers of dissimilar alkylene oxides such as copolymer ethylene oxide and 1,2-propylene oxide (poly(oxyethylene-1,2-oxypropylene)glycol), as well as I monoethers and monoesters thereof, preferably at oxide ratios of from 75:25 to 10:90 ethylene oxide to 1,2-

, propylene oxide, and molecular weight of from about 250 erably have from 1 to about 10 carbon atoms, While the monocarboxylic acids preferably have from 1 to 12 carbon atoms.

The following compositions are representative of the invention, which can be used neat or diluted with from 1 to 10, preferably 1 to 10 parts of water, as metalworking lubricants for cutting, drilling and the like. The concentrations are molar.

Composition A:

Sodium thiosulfate 0.1 M

Hydroxylamine 0.1 M Composition B:

Sodium hydrosulfite 0.1 M

Hydroxylamine 0.1 M Composition C:

Potassium pcrsulfate 0.1 M

Hydroxylamine 0.1 M

3 Composition D:

Sodium thiosulfate 0.1 M

Glucose 0.1 M Composition E:

Sodium thiosulfate 0.1 M

Hydroxylamine 0.1 M

Triethanolamine 2% wt.

Hetero-copolymer of ethylene oxide-1,2 propylene oxide (75/25), visc. 450/ 100 F wt. Composition F:

The outstanding properties of compositions of this invention were demonstrated by subjecting them to the following tests:

(1) Four-ball machine test as described in the Journal of the Institute of Petroleum Technology, pages 206229, April 1946.

(2) Tool life test.--The compositions were used as lubricants in drilling 1 holes in A181 4340 steel and the number of holes drilled to failure of tool was noted.

(3) Rust test.-Cast iron strips were immersed in the test lubricant for 24 hours and the strips were then removed and assigned a rust rating of A=none, B=trace, C=moderate, Dzheavy.

Compositions A-K in the four-ball test gave average weld load (kg) values of between 600 and 800, averaged around 175 holes drilled in the tool life test and in the rust test gave a rating of A. When the reducing agents were omitted from compositions A-K and the salt concentration increased to 0.2 M, the average weld load (kg) varied between 300-400 kg. Also, when the salts were omitted from compositions A-K and the amount of reducing agent adjusted to 0.2 M the average weld load (kg) was reduced to 100-200 kg. Also, in each case when one or the other of the two essential additives were omitted from compositions AK the tool life was reduced to approximately 30-35 holes drilled.

Compositions of this invention may contain additional additives, such as water-soluble corrosion inhibitor, e.g., sodium mercaptobenzothiazole, anti-foaming agents such as silicone polymer, perfuming agents, and dyes. The

compositions may be applied with excellent results to general cutting operations Where cooling and lubricating of the tool and work piece under adverse conditions are encountered. Metals machined with the aid of fluids of this invention have good surface finish, are free from rust and the cutting tool life is excellent.

I claim as my invention:

1. An aqueous metal-working lubricant consisting essentially of a major amount of water and from about 0.05 to about 5 moles per liter of water each of (1) a water-soluble sulfur-containing alkali metal salt selected from the group consisting of alkali metal thiosulfate, alkali metal hydrosulfite, alkali metal persulfate, alkali metal thiodiacetate and (2) a hydroxyl-containing reducing agent selected from the group consisting of 'hydroxylamine, glucose, lactose, resorcinol, pyrogallol and phloroglucinol.

2. An aqueous metal-working lubricant consisting essentially of a major amount of Water and from about 0.1 to 1 mole per liter of Water each of sodium thiosulfate and hydroxylamine.

3. An aqueous metal-working lubricant consisting essentially of a major amount of water and from about 0.1 to 1 mole per liter of Water each of sodium thiodiacetate and hydroxylamine.

4. An aqueous metal-working lubricant consisting essentially of a major amount of water and from about 0.1 to 1 mole per liter of water each of sodium thiodiacetate and phenyl hydroxylamine.

5. An aqueous metal-Working lubricant consisting essentially of a major amount of water and from about 0.1 to 1 mole per liter of water each of sodium thiodiacetate and pyrogallol.

6. The lubricant composition of claim 2 containing from about 2% to about 10% by weight each of Watermiscible hetero-copolymer of ethylene oxide and 1,2-propylene glycol, and an ethanolamine.

7. The lubricant composition of claim 3 containing from about 2% to about 10% by weight each of water miscible hetero-copolymer of ethylene oxide and 1,2-propylene glycol, and an ethanolamine.

8. The lubricant composition of claim 4 containing from about 2% to about 10% by weight each of watermiscible hetero-copolymer of ethylene oxide and 1,2-propylenc glycol, and an ethanolamine.

9. The lubricant composition of claim 5 containing from about 2% to about 10% by weight each of watermiscible hetero-copolymer of ethylene oxide and 1,2-propylene glycol, and an ethanolamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,063,297 Crabtree et al. Dec. 8, 1936 2,588,234 Henricks Mar. 4, 1952 2,981,686 Reamer Apr. 25, 1961 FOREIGN PATENTS 807,660 Great Britain Jan. 21, 1959 

1. AN AQUEOUS METAL-WORKING LUBRICANT CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF WATER AND FROM ABOUT 0.05 TO ABOUT 5 MOLES PER LITER OF WATER EACH OF (1) A WATER-SOLUBLE SULFUR-CONTAINING ALKALI METAL SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL THIOSULFATE, ALKALI METAL HYDROSULFIDE, ALKALI METAL PERSULFATE, ALKALI METAL THIODIACETATE AND (2) A HYDROXYL-CONTAINING REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF HYDROXYLAMINE, GLUCOSE, LACTOSE, RESORCINOL, PYROGALLOL AND PHLOROGLUCINOL. 